Indicator for electrode clamping mechanism



C. w. VOKAC INDICATOR FOR ELECTRODE CLAMPING MECHANISM Filed Aug. 11, 1966 July 16, 1968 2 Sheets-Sheet l $03 02 O all in Jam.

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July 16, 1968 c. w. VOKAC INDICATOR FOR ELECTRODE CLAMPING MECHANISM 2 Sheets-Sheet 2 Filed Aug. 11, 1966 I N VENTOR.

United States Patent 3,393,265 INDICATOR FOR ELECTRODE CLAMPING MECHANISM Charles W. Vokac, Flossmoor, Ill., assignor to Whiting Corporation, a corporation of Illinois Filed Aug. 11, 1966, Ser. No. 571,942 2 Claims. (Cl. 13-16) ABSTRACT OF THE DISCLOSURE One end of an indicating rod is secured to the fluid operated piston which applies clamping pressure to the electrode. The other end of this rod extends exteriorly of the mechanism in adjacent relation with the stud end of a fastener. An adjustable stop is provided to limit the amount of movement of the piston in applying clamping pressure. The stud end of the fastener is moved in response to adjustment of the stop. The stud end serves as a reference to indicate the limit of travel of the piston in applying clamping pressure, the function of the stud end as such an indicator being unaffected by adjustment of the stop.

This invention relates in a general way to mechanism for adjustably mounting an electrode for use in an electric arc furnace, and more particularly the invention relates to indicator means for indicating when the stroke of movement of certain members of such mechanism have reached a predetermined limit.

By way of background, the present invention has to do with improvements in the nature of indicator means for use with mechanism adapted adjustably to mount an electrode in an electric arc furnace. Such mechanism includes a horizontally mounted arm having one end thereof disposed over an electric arc furnace. This end of the arm mounts a head having a vertically oriented, through opening for receiving an electrode. A shoe member is arranged in the opening in the head member for clamping engagement with an electrode therein. A push rod extending longitudinally of the arm has one end thereof engaged with the shoe and the other end thereof associated with a piston, which piston is mounted in a fluid pressure chamber. Fluid pressure in this chamber acts on the piston and thereby urges the shoe in clamping engagement with the electrode for holding the same with the lower end thereof in the electric arc furnace. As the electrode is expended during use, the same is adjusted or lowered vertically by reducing the pressure on the piston thereby allowing the electrode to creep downwardly by its own weight and under the control of an operator.

Certain operational and design considerations require the stroke of the piston to be quite limited in relation to the diameter of the electrode, which is made'from either graphite or carbon. As is known to those skilled in the art, such electrodes are not made to close tolerances, with respect to diameter. Further, such electrodes frequently have low spots along their lengths. A low spot is a flat spot in a localized area of the electrode. It is possible for the piston to travel too far, i.e., bottom-out, for a number of reasons, such as: the diameter of the electrode may be too small with respect to the diameter of the head member of the clamping mechanism; the shoe may engage a low spot on the electrode; the various parts in the head mechanism which contact the electrode may wear; the various members of the clamping mechanism may change in dimensions by reason of wear and by reason of being subjected to heat and pressure. In any of these instances, a situation may result whereby the requisite amount of clamping pressure will not be applied to the electrode by the shoe thereby allowing the former to slip or drop into ice the electric arc furnace, or to become loose, to overheat and deteriorate, all of these results being of course quite undesirable. Should the diameter of an electrode be too small with respect to the diameter of the head member of the clamping mechanism, or should the shoe engage a low spot on the electrode, it is possible for the piston to travel too far, i.e., bottom-out, in which case the requisite amount of clamping pressure will not be applied to the electrode by the shoe and the former may slip or drop into the electric arc furnace which is of course undesirable. Accordingly, there is a need in such a clamping mechanism for a means to indicate readily when the piston is approaching a predetermined limit of travel, which limit is established by the bottoming-out position of the piston.

A primary object of the present invention is the provision of unique and simple means to indicate when the piston in a mechanism of the type described approaches a predetermined limit, so that appropriate steps can be taken to prevent bottoming-out or overtravel of the piston.

Another object of the present invention is the provision of indicator means according to the foregoing object, wherein such indicator means includes and makes advantageous use of certain members which form part of the electrode mounting mechanism itself.

Still another object of the present invention is the provision of indicator means in an electrode clamping mechanism which includes means, such as shims, to compensate for wear of the parts which grip the electrode, wherein the indicator means are independent of and unaffected by operation of such compensating means.

These and other objects and advantages of the invention will become apparent from the following specification disclosing a preferred embodiment of the invention illustrated in the accompanying drawings wherein:

FIG. 1 is a side elevational view of an electrode clamping mechanism in which the present invention is incorporated;

FIG. 2 is an enlarged section taken along the line 2-2 of FIG. 1;

FIG. 3 is an enlarged section of the fluid pressure assembly of the mechanism illustrated in FIG. 1, with only the parts above the centerline of the push rod being shown; and

FIG. 4 is an enlarged section taken along the line 44 of FIG. 2.

Referring now to FIG. 1, the electrode clamping mechanism will be seen to include a hoizontally disposed arm 10 which is defined by a casting 10a and a coaxial insulator 10c separating the former from a coaxial tubular extension 1012, the latter being water-cooled at the electrode end. The arm 10, which is hollow, mounts a head 12 at the Water-cooled end thereof. This head, usually of one piece, high conductivity, copper and also of watercooled construction, includes a vertically extending opening 14 (FIG. 2) for receiving an electrode 15. The electrode, made of graphite or carbon material, is supported in the head 12 with the lower end of the electrode in an electric arc furnace (not shown). The casting 10a includes a plate 16 adapting the casting for mounting on the upper end of a mast which is mounted adjacent the furnace.

The clamping mechanism further includes a bus tube 18 mounted in insulated relation at one end thereof by an integral extension 19 of the casting 10a. The other end of the bus tube is solidly mounted by a formation 20 integral with the head 12. This bus tube contains the necessary electrical conductors for conducting current to the electrode held by the head.

A clamping shoe 22 has an arcuate face 22a adapted for engagement with the surface of the electrode 15 thereby to hold the latter in the opening in the head 12.

3 As best noted in FIG. 4, the shoe 22 includes an integral extension 22b Which is received within an insulating tubing 24. This tubing 24 is mounted within suitable means, designated 25, thereby supporting the shoe for slidable movement to and away from the electrode in a direction longitudinally of the arm The integral extension 2212 of the shoe includes a blind bore in which another insulating sleeve 27 is received. An insulating plug 28 is provided in the base of the blind bore in the extension 22b of the shoe. A push rod 30 has a reduced-in-diameter portion 30a at one end thereof, which portion is received within the sleeve 27 with the end of the portion 30a in abutting engagement with the insulating member 28. Sleeve 27 and member 28 insulate the shoe 22 (which is in direct contact with the electrode) from the push rod 30.

As noted in FIG. 1, the push rod 30 extends longitudinally of the arm 10 within the same. Referring now to FIG. 3, the other end of the push rod 30 will be seen to abut a piston plate 31. This piston is mounted within a fluid pressure chamber 32 defined by a housing member 33 connected to an annular plate 34, which plate is mounted to the adjacent end of arm 10. The housing 33 includes an annular flange 33a. The housing 33 is secured to the plate 34 by a plurality of fasteners 36 arranged in a circumferential pattern and extending through suitable bores in the plate 34 and the flange 33a. One or more shims 37 may be arranged between the plate 34 and the flange 33a. Also arranged between the plate 34 and the flange 33a is a thin annular flange 39a of a plate 39. This plate is provided with a central opening 3% forming a bearing surface for the end of the push rod 30 adjacent the piston 31.

A bellows 40 has one end thereof connected to the piston 31 and the other end thereof connected to the plate 39. Fluid under pressure is admitted into the fluid pressure chamber 32 from a hose or fitting 42 (FIG. 1), such hose or fitting being connected to a suitable source of fluid, such as air, under pressure. Fluid pressure in the chamber 32 urges the piston to the left and this in turn urges the shoe 22 against the electrode for holding the same in place in the head 12. The electrode may be lowered as the same is expended during use by lowering the air pressure and thereby allowing the electrode to creep downwardly under its own Weight and under the control of an operator. As mentioned above, certain operational and design consideration require the stroke of the piston and of the push rod to be quite limited in relation to the diameter of the electrode. For example, in a mechanism adapted to support an electrode of ten to eighteen inches in diameter, the stroke of the push rod is in the order of an inch to two inches. Movement of the piston 31 to the left is limited by its engagement with a cylindrical member 44 coaxial with the push rod and having one of its ends secured to the plate 39.

It is believed that the above description of the nature and operation of the electrode mechanism will suffice for purposes of understanding the present invention. For a more detailed explanation of the operation of an electrode clamping mechanism of this type, reference may be had to United States Patent No. 2,386,260 to W. H. Payne.

As mentioned above, the electrodes used in the above described mechanism are not made to close tolerances and frequently have low spots. Accordingly, an electrode having a nominal diameter designed to be received within the opening 14 in the head 12 may have an actual dimeter smaller than the nominal diameter in which case the piston 31 may bottom-out, i.e., strike the end of the member 44' as fluid pressure is admitted to the chamber 32 to urge the shoe in clamping engagement with such an electrode. Also, even though an electrode might have an actual diameter such that it can be clamped in the opening in the head 12, a flat or low spot may be encountered during downward progression of the electrode in which case thepiston 31 could bottom-outf should the piston bottom-out, the requisite pressure cannot of course be applied to the electrode from the shoe 22, and under such circumstances the electrode may be dropped into the associated electric arc furnace. Another factor which aggravates this problem of bottoming-out of the piston 31 is the wear of the surfaces of head 12 and shoe 22 where they contact the electrode 15. These parts and others also change dimensions when subjected to clamping pressures and heat (from the furnace and the electrical circuitry), further aggravating the problem of bottoming-out of the piston 31. The present invention provides for a unique and simple means to indicate to an operator of the electrode mechanism when the piston is approaching its limit of travel, i.e., approaching the end of the sleeve 44.

An indicator pin 46 extends in parallel relation with the push rod 30 and has one end thereof secured to the piston 31. The pin 46 extends through coaxial openings 39c and 34a in the plates 39 and 34, respectively, the other end of the indicator 46 being disposed exteriorly of the electrode clamping mechanism for observation by an operator. Gauge means to indicate the limit of movement of the pin 46 and thereby the limit of movement of the piston 31 are conveniently provided by having one of the fasteners 36, namely the fastener 36' in FIG. 3, somewhat greater in length than the other fasteners. When the exterior end of the pin 46 is contained within a vertical plane which also contains the stud end of the fastener 36, the piston 31 will have almost reached its limit of travel determined by the end of the member 44. Therefore, if an operator of the electrode mechanism notices the end of the pin 46 being more or less in vertical alignment with the stud end of the fastener 36, he knows the piston 31 is very close to bottoming-out. The operator can then take steps to prevent bottoming-out of the piston, such as by removing one or more of the shims 37, thereby moving the stop 44 to the left for increasing the stroke of the piston 31. Removal of a shim will of course result in movement of the fasteners 36 to the left a distance corresponding to the amount of movement of the stop 44. Therefore, it will be noted that such adjustment does not affect operation of the pin 46 in indicating the position of the piston.

It may also be desirable to indicate the other limit of travel of the piston 31, i.e., the limit defined by engagement of the piston 31 with the inside of housing member 33. This may be achieved by arranging one or more of the other fasteners 36 so that their stud ends will occupy the same vertical plane with the outer end of the indicator pin 46 when the piston occupies this other limit of its travel. In such case, the fasteners 36, 36 indicate the stroke of the piston, the position of the piston along its stroke being indicated by the relationship of the indicator 46 to these fasteners.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not to be so limited. On the contrary, the invention is susceptible of various forms and modifications without departing from the spirit and scope of the appended claims.

I claim:

1. In combination with a mechanism for adjustably mounting an electrode for use in an electric arc furnace, which mechanism includes an arm supporting at one end thereof a head which defines an opening for receiving an electrode, a shoe arranged adjacent said head for clamping engagement with an electrode in the opening therein, and which mechanism also includes a clamping assembly movable longitudinally of said arm and consisting of a push rod having one end thereof engaged with said shoe, and a piston engaged with the other end of said push rod, said mechanism further including means for applying fluid pressure to said piston thereby to urge said shoe in clamping engagement with an electrode, stop means including an adjustable stop for limiting movement of the piston toward said head, means defining a gauge element, which gauge element is disposed exteriorly of said mechanism and is movably axially of said arm in response to adjustment of said stop, the direction of movement of the gauge element when so moved corresponding to the direction of movement of the stop, an indicator member secured to said piston for movement therewith and having a portion in adjacent relation with said gauge element, which gauge element serves as a reference to indicate the limit of travel of said piston toward said head.

2. In combination with a mechanism for adjustably mounting an electrode for use in an electric arc furnace, which mechanism includes an arm supporting at one end thereof a head which defines an opening for receiving an electrode, a shoe arranged adjacent said head for clamping engagement with an electrode in the opening therein, and which mechanism also includes a clamping-assembly movable longitudinally of said arm and consisting of a push rod having one end thereof engaged with said shoe, and a piston engaged with the other end of said push rod, the mechanism further including fluid operated means for applying pressure to said piston thereby to urge said shoe in clamping engagement with an electrode, said fluid operated means including a housing enclosing said piston, which housing is defined in part by a first annular plate fixedly mounted by said mechanism in perpendicular relation with said arm, a second annular plate in said housing in intermediate parallel relation with said first plate and said piston and carrying a stop to limit movement of the shoe, a plurality of shims disposed between said first and second annular plates, fastening means drawing said first and second plates together with said shims therebetween, which fastening means include a bolt extending in parallel relation with said arm and having the stud end thereof disposed exteriorly of said housing, whereby said bolt is positioned axially of said arm in response to the number of shims between said annular plates, an indicator rod extending in parallel spaced relation with said arm and having one end thereof secured to said piston, the other end of said rod being disposed exteriorly of said housing in adjacent relation with said stud end whereby the latter serves as a reference to indicate the limit of travel of said piston in urging said shoe against an electrode.

References Cited UNITED STATES PATENTS 2,249,776 7/1941 Moore 13-16 2,386,260 10/1945 Payne 13-16 2,538,603 1/1951 Thys 13- -16 BERNARD A. GILHEANY, Primary Examiner. I

H. B. GI-LSO-N, Assistant Examiner. 

